Nephrotic syndrome is a kidney disorder that causes your body to excrete too much protein in your urine.
Nephrotic syndrome is usually caused by damage to the clusters of tiny blood vessels (glomeruli) of your kidneys.
The glomeruli filter your blood as it passes through your kidneys, separating things your body needs from those it doesn't. Healthy glomeruli keep blood protein (mainly albumin) — which is needed to maintain the right amount of fluid in your body — from seeping into your urine. When damaged, glomeruli allow too much blood protein to leave your body, leading to nephrotic syndrome.
Many possible causes
Many diseases and conditions can cause glomerular damage and lead to nephrotic syndrome, including:
Minimal change disease. The most common cause of nephrotic syndrome in children, this disorder results in abnormal kidney function, but when the kidney tissue is examined under a microscope, it appears normal or nearly normal. The cause of the abnormal function typically can't be determined.
Focal segmental glomerulosclerosis. Characterized by scattered scarring of some of the glomeruli, this condition may result from another disease or a genetic defect or occur for no known reason.
Membranous nephropathy. This kidney disorder is the result of thickening membranes within the glomeruli. The exact cause of the thickening isn't known, but it's sometimes associated with other medical conditions, such as hepatitis B, malaria, lupus and cancer.
Diabetic kidney disease. Diabetes can lead to kidney damage (diabetic nephropathy) that affects the glomeruli.
Systemic lupus erythematosus. This chronic inflammatory disease can lead to serious kidney damage.
Amyloidosis. This disorder occurs when substances called amyloid proteins accumulate in your organs. Amyloid build up often affects the kidneys, damaging their filtering system.
Blood clot in a kidney vein. Renal vein thrombosis, which occurs when a blood clot blocks a vein connected to the kidney, can cause nephrotic syndrome.
Heart failure. Some forms of heart failure, such as constrictive pericarditis and severe right heart failure, can cause nephrotic syndrome.
Signs and symptoms of nephrotic syndrome include:
Severe swelling (edema), particularly around your eyes and in your ankles and feet.
Foamy urine, which may be caused by excess protein in your urine.
Weight gain due to excess fluid retention.